f  7.±i 


LAft   No.   112. 

I  iiitcil  Stat( 


0\Uj 


F 


V  o^ 


■ 


>anment  of  Agriculture, 

Ot*   KNTOMOUOGY, 


ARD.  Entomologist  and  Chief  of  1 


CONTROL  OF  THE  MEDITERRANEAN   FLOUR   MOTH   BY 
HYDROCYANIC-ACID  <;AS   FUMIGATION. 

Bj    I     II    «  mil  i  \i'i  s.  Si     1 1  . 
In  Char  '  Crop  and  Stored  Prodv 

I  vi  i;<  >i>i  (   i  OBI  . 

Until  in  Bomewhat  recent  years  Qour  mills  in  the  United  States 
were  little  troubled  with  injurious  insects.  It  is  true  thai  weevils 
and  other  granary  pests  were  brought  into  the  mills  with  grain,  and 
in  tlic  course  of  time  many  mills  have  become  infested  with  Qour 
beetles       Beginning   with    the   year    1892,    however,   several   Cali- 


FM    1       MwUfTllWll  fllHIl  lllllttl  (  ITjltl»ffcl  tmtntlffn)     a.  Moth;'). 
same  from 
oflana.     id   Knlaro"!   r moriM-n!.  thor's Illustration.) 


PIG     -'      M.'.liicrrancan 
Hour    moth:     i 
dorsal     Haw.      (Au- 
thor's i  ll<  i 


fornia  mills  became  infested  by  the  Mediterranean  Hour  moth 
(Ephettia  kuehirieUa  Zell.),  which  has  been  aptly  called  "the  scourge 
of  t  he  Hour  mill  "  and  t  he  "  winged  gray  plague."  At  first  its  prog] 
in  this  country  was  slow,  hut  in  lees  than  a  decade  it  had  become 
recognized  as  a  most  Berious  pest  in  many  States,  and  at  the  present 
time  it  is  known  to  occur  in  practically  all  of  om-  principal  milling 
centers,  and  in  most  of  our  States  from  the  Atlantic  to  the  Pacific 
and  from  Canada  to  Mexico. 


"  Chiefly  speciec  ol  Tribolium,  Ctenocori 

Cir   ii-_>— 10 1 


DEPC 


Descriptive. — The  adult  insect  is  a  phycitid  moth  with  a  wing 
expanse  of  a  little  less  than  an  inch;  the  fore-wings  are  pale  leaden 
gray,  with  transverse  black  markings  of  the  pattern  shown  in  the 

accompanying  illustration  (fig.  1,  a);  the  hind-wings  are  dirty 
whitish,  semitransparent,  and  with  a  darker  border.  The  larva  or 
caterpillar,  illustrated  at  figure  1,  c,  ( ,  and  at  figure  2,  is  whitish  with 
minute  black  dots,  and  sparsely  hairy.  When  full  grown  it  measures' 
about  one-half  an  inch  or  a  little  longer  (12.5-17.5  mm.).  The 
chrysalis,  shown  at  figure  1,  d,  is  reddish  brown. 

Distribution. — Until  the  year  1S77,  when  the  moth  was  discovered 
in  a  flour  mill  in  Germany,  this  insect  was  comparatively  unknown. 
Later  it  invaded  Belgium  and  Holland,  and  in  1886  appeared  in 
England.  Three  years  afterwards  it  made  its  appearance  in  destruc- 
tive numbers  in  Canada.  In  1892  it  was  reported  injurious  in  mills 
in  California,  and  in  1895  in  New  York  and  Pennsylvania. 

From  that  time  forward  until  1904  the  dissemination  of  the  species 
was  comparatively  slow.  In  1898  it  had  reached  Minnesota,  the 
next  year  Wisconsin;  in  1900  it  had  greatly  increased  in  Minnesota: 
two  years  later  it  invaded  Michigan,  and  by  1904  it  was  reported  in 
several  other  States,  including  Indiana,  Illinois,  Montana,  Colorado, 
Ohio,  and  Iowa.  In  later  times,  each  year  has  witnessed  a  similar 
increase  in  distribution,  until  now,  in  1910,  this  flour  moth  is  attract- 
ing more  attention  than  any  insect  that  ever  infested  mills  or  other 
buildings  where  cereals  are  stored;  indeed,  it  is  almost  the  sole  topic 
of  complaint  of  millers  at  the  present  writing,  correspondence  in 
regard  to  weevils  and  flour  beetles,  which  was  at  one  time  heavy, 
having  fallen  off  very  noticeably. 

Ravages  and  habits. — The  caterpillars  form  cylindrical  silken  tubes 
in  which  they  feed,  and  it  is  largely  due  to  their  habit  of  web  spinning 
that  they  are  so  injurious  where  they  obtain  a  foothold.  Upon 
attaining  full  growth  the  caterpillar  leaves  its  original  silken  domi- 
cile and  forms  a  new  web,  which  becomes  a  cocoon,  in  which  it 
undergoes  transformations  to  pupa  and  to  imago.  While  searching 
for  a  place  for  transformation  the  insect  is  most  troublesome.  The 
infested  flour  becomes  felted  together  and  lumpy,  the  machinery 
becomes  clogged,  necessitating  frequent  and  prolonged  stoppage,  and 
resulting  in  a  short  time,  in  large  establishments,  in  the  loss  of  thou- 
sands of  dollars.  A  sample  of  matted  flour  is  illustrated  in  figure  3, 
from  a  photograph  by  Mr.  C.  H.  Popenoe. 

As  to  the  losses  caused  directly  and  indirectly  by  this  insect  it  has 
been  difficult  to  obtain  estimates,  the  lowest  being  between  $100 
and  $200  to  a  mill  of  1,000  barrels  capacity.  The  average  loss  due 
to  closing  down  the  mill  and  cost  of  treatment  seems  to  be  not  far 
from  $500  for  each  fumigation,  ''to  say  nothing  of  the  loss  to  busi- 
ness," according  to  one  Kansas  milling  firm.  An  estimate  of  $1,000 
[Cir.  112] 


for  two  fumigations  can  oof  be  far  from  right,  although  others  esti- 
mate SJ, t,  while  »\\\\  others     n«  QeTS  of  larger  mills      claim  it  to  be 

15,000  a  year.    One  prominent  miller  states  thai ,  aside  from  the  cost 


\2           ^^W 

Mm 

LiBfc  ft**3M 

*  >       '?  1 

''^B 

PWa\l 

'  *«HI 

T 

.<■ 

«                   *( 

^a.  ^^Br         t 

- 

H*           ^iiiiiiife. 

^B 

1 

Flo.  3-  Mattel  flour  showing  the  work  of  the  Mediterranean  flour  moth.    (Original.) 

of  fumigating,  the  loss  due  to  Btoppage  w  bile  cleaning  is  incalculable, 
ami  expresses  the  opinion  that  some  restrictions  should  be  imposed 

on  millers  who  tlo  not  clean  and  fumigate  their  mills. 


[Or.  IIS] 


Although  thr  Larva  prefers  Hour  or  meal,  it  will  attack  grain  when 
the  former  are  not  available,  and  it  flourishes  also  on  bran  and  pre- 
pared  eereal  foods,  including  buckwheat,  grits,  and  crackers.  It  lives 
also  in  the  nests  of  bumblebees  and  in  the  hives  of  the  honey  bee. 

FIRST    USE    OF   HYDROCYANIC-ACID    GAS    AGAINST    INSECTS    IN    STORED 

PRODUCTS. 

The  use  of  hydrocyanic-acid  gas  as  a  remedy  for  insects  in  mills 
and  other  inclosures  whore  grain,  flour,  and  similar  products  are 
stored  was  first  suggested  by  the  late  "\Y.  G.  Johnson  in  the  American 
Miller  for  March,  1898,  the  incentive  for  its  employment  having  been 
an  invasion  of  cockroaches  in  a  mill  in  North  Carolina. 

The  first  test  of  this  method  as  a  means  of  destroying  insects  in 
stored  products  was  probably  that  made  by  the  writer  the  same  year.0 

Additional  experiments  were  soon  afterwards  made  in  conjunction 
with  Mr.  Pratt  and  the  cost  and  the  advantages  and  disadvantages 
carefully  weighed,  with  the  resulting  conclusion  that  since  hydrocy- 
anic-acid gas  is  infinitely  more  dangerous  to  human  life  than  bisulphid 
of  carbon,  as  well  as  more  expensive,  its  employment  as  a  fumigant  for 
ordinary  insects  injurious  to  stored  products  was  less  desirable.  On 
this  account  no  publication  was  made  of  the  results  nor  was  it,  until 
recently,  recommended  to  the  numerous  persons  who  inquired  for 
remedies  for  mill  pests.  Soon  after  this  first  experiment  a  test  to 
determine  the  availability  of  this  gas  against  the  Angoumois  grain 
moth  was  made  on  a  larger  scale  but  with  very  imperfect  success.6 

a  March  5,  1898,  the  writer,  with  Mr.  F.  C.  Pratt,  then  working  under  his  direc- 
tion, fumigated  a  lot  of  dried  grain  infested  by  the  rice  weevil  (Calandra  oryza  L.) 
and  a  leguminous  seed  affected  by  a  Bruchus  or  seed  weevil,  the  material  being  placed 
in  a  moderately  tight  fumigating  box.  The  cyanid  of  potash  was  purchased  in  open 
market  and  was  used  at  the  rate  of  2  ounces  to  each  100  cubic  feet.  A  quantity  of 
acid  slightly  in  excess  of  the  salt  was  employed  with  twice  that  amount  of  water. 
The  experiment  began  at  4  p.  m.  Saturday  and  was  conducted  in  a  building  in  which 
the  temperature  was  usually  from  70°  to  76°  F.  The  following  Monday  morning  at 
7.30,  when  the  door  was  opened  for  airing,  no  odor  was  perceptible,  and  only  a  very 
slight  trace  of  gas  could  be  detected  a  half  hour  later  when  the  box  lid  was  removed. 
As  a  result  all  the  seed  weevils  (Bruchus)  loose  in  bags  were  found  dead  and  all  of 
the  rice  weevil,  except  a  very  few  individuals,  which  revived  after  a  few  hours — 
less  than  0.1  per  cent — were  killed. 

*>  A  lot  of  paddy  or  unhulled  rice  infested  by  this  moth  was  desired  to  be  fumigated 
and  was  placed  in  what  appeared  to  be  a  nearly  air-tight  inclosure,  a  room  specially 
prepared  for  the  purpose.  The  cyanid  was  prepared  in  the  usual  way  and  was  used 
at  a  strength  of  about  1  ounce  to  100  cubic  feet,  but  after  the  fumigation  the  insects 
were  seen  to  be  flying  freely  about  the  fumigating  room.  See  Bureau  of  Entomology 
Cir.  No.  46,  entitled,  "Hydrocyanic-acid  Gas  against  Household  Insects,"  by  L.  0. 
Howard,  first  issued  in  1902,  revised  edition  February  20,  1907.  Note  what  is  said 
in  the  footnote  on  page  2. 
[Cir.  112] 


During  1899  mill>  were  fumigated  in  Pennsylvania  and  <  >lii",  under 
the  direction  of  Professor  Johnson,  with  Bal  isf  actor}  results,  and  con 
tinued  in  later  years  b)  and  under  the  direction  oi  Professor  Johnson 
well  a>  l>\  Professor  Washburn,  State  entomologist  of  Minnesota,  Prof. 
II  \  Surface,  State  zoologist  of  Pennsylvania,  and  other  State 
officials.  In  the  course  of  time  hydrocyanic-acid  gas  has  come  to  be 
recognized  as  the  besl  fumiganl  for  the  Mediterranean  Sour  moth.  Ii 
i>  equally  valuable  against  related  moths  found  in  mills,  l>ut  i-  le~^ 
effective  in  destroying  flour  beetles  and  grain  weevils,  and  even  in 
the  destruction  <>f  the  Angoumois  grain  moth  in  corn.  Indeed,  it  is 
not  general!)  recommended  for  any  of  the  latter  pests. 

Prom  what  subsequently  has  been  learned  of  tlii-  method,  failure 
in  some  cases  was  undoubtedly  « I im>  to  impure  potassium  cyanid  and 
to  faulty  application  of  the  process,  since  the  fumigating  vessels  were 
rather  small  for  the  purpose  and  permitted  a  considerable  boiling 
over  at  the  t>>p.  Much  residue  also  remained;  in  other  words,  the 
potassium  cyanid  was  probablj  too  weak,  perhaps  no  stronger  than 
.">n  to  60  per  cent  pure,  as  was  also  the  sulphuric  acid,  which  was  not 
used  in  sufficient  quantity  to  produce  a  perfect  gas,  a  considerable 
amount  of  cyanid  remaining  unaffected  as  solid  residue  in  the  generat- 
ing vessel.  It  seems  also  probable  thai  the  cyanid  was  broken  into 
too  line  particles,  but  this  detail  can  not  now  he  remembered. 

Owing  to  these  failure--  as  well  as  to  t  hose  of  other  tests  which  were 
afterward-  made,  the  suspicion  arose  that  something  was  wrong  with 
the  ingredients.  A  sample  of  the  cyanid  used  was  submitted  to 
the  Bureau  of  Chemistry  and  treated  with  sulphuric  acid,  with  the 
result  that  only  54.50  per  cent  of  the  amount  of  hydrocyanic-acid 
gas  demanded  by  theory  was  found.  Analysis  showed  51.70  per 
cent  potassium  cyanid.  2.1)7  per  cent  sodium  cyanid.  and  .'!'.>. 28  per 
cent  potassium  carbonate,  the  remainder  consisting  of  sodium  chlo- 
i id  or  common  salt  and  impurities.  It  will  be  noticed  that  this 
cyanid  was  little  more  than  half  a-  strong  a-  demanded  for  per- 
fect work;  hence,  what  appeared  t"  he  a  fumigation  at  the  rate  of 
30  ounces  t<>  1,000  cubic  feet  was  in  reality  only  about  16  ounc< 


"  An  instance  oi  fumigation  with  impure  cyanid  of  potash  should  be  cited.  During 
September,  1904,  th«'  writer,  with  Mr  Pratt,  undertook  the  fumigation  of  a  dwelling 
infested  by  thi  if  cyanid 

to  100 cubic  i'  •  .  which  destroyed  man}  I ties     Two  weeks  later,  however, 

the  beetles  bad  again  accumulated  in  numbers,  showing  th.it  neither  larva-  nor  pups 
had  been  killed  to  an}  •  rhen  3  ounces  of  cyanid  were  used  with  a  still  loi 

.i  total  of  practically  forty-two  bout  killed  many  larva  which 

dropped  from  the  furniture,  the  principal  -eat  of  infestation,  although  carpets  were 
also  affected,  but  many  were  probably  not  killed  inly  the  eggs  wen 

destroyed,  as  the  insects  continued  t..  infesl  the  house,  with  the  result  that  bef  i 
third  fumigation  could  !»•  given  the  furniture  was  disposed  of 

For particulai  -  :o.  Bui.  ">i.  Bur.  But.,  I     S.  Dep(    Agi     . 

[Or.  112] 


It  should  not  be  imagined  that  because  this  method  is  of  value 
against  the  Mediterranean  flour  moth  and  related  insects,  and  soft- 
bodied  species  like  psocids  or  book-lice,  which  also  occur  in  mills, 
that  it  is  a  sovereign  remedy  for  other  insects  in  mills  and  other 
inclosures.  Quite  the  contrary;  it  has  been  found  only  partially 
effective  and  therefore  unsatisfactory  when  used  against  grain 
weevils,  flour  beetles,  and  other  hard-bodied  insects,  and  the  pre- 
paratory stages  of  the  Angoumois  grain  moth,  although  effective 
in  killing  the  adults  of  the  latter.  Indeed,  not  until  very  recent 
years  has  its  use  become  generally  recommended  for  the  flour  moth. 

Mr.  C.  H.  Popenoe,  working  under  the  writer's  direction,  in  fumi- 
gating primarily  for  the  flour  moth,  succeeded  in  killing  many  of  the 
confused  flour  beetle  (Tribolium  confusum  Duv.)  in  two  application- 
at  4  ounces  to  1,000  cubic  feet.  A  larger  percentage  was  destroyed 
by  one  application  at  the  rate  of  S  ounces,  and  so  on  up.  Mr.  D.  K. 
McMillan  had  similar  good  success  with  10  ounces. 

In  pamphlets  published  in  1904  Prof.  F.  L.  Washburn  has  rec- 
ommended hydrocyanic-acid  gas  for  the  treatment  of  the  flni'- 
moth,  stating  the  advantages  of  this  treatment  and  giving  details 
as  to  the  penetrating  power  of  the  gas  and  other  matters.0 

As  an  instance  of  the  successful  use  of  hydrocyanic-acid  gas,  the 
experience  of  a  Kentucky  milling  firm  that  was  advised  to  use  this 
method  of  fumigation  may  be  briefly  narrated. 

In  the  city  where  this  firm  is  located  the  species  had  been  present 
in  their  mill  four  years,  yet  a  few  months  prior  to  hearing  from  them 
the  writer  did  not  know  of  the  insects'  occurrence  in  that  State.  It 
had  been  introduced  in  second-hand  machinery.  Bisulphid  of  carbon 
had  been  used  by  them  previous  to  their  correspondence  with  the 
writer  and  was  described  as  "no  good  except  for  weevils  in  stored 
grain."  It  had  been  employed  at  the  rate  of  300  pounds  to  62,400 
cubic  feet  of  air  space,  or  about  5  pounds  to  1,000  cubic  feet — fully 
twice  as  strong  as  necessary  in  an  ordinary  mill.  Afterwards,  by  the 
writer's  advice,  hydrocyanic-acid  gas  was  employed  and  the  follow- 
ing report  was  made,  August  24,  1909: 

Saturday,  July  24,  1909,  our  mill  was  fumigated  with  hydrocyanic-acid  gap,  using 
18  4-gallon  jars,  each  charged  with  3  pounds  (if  cyanid  of  potassium,  4J  pounds  of 
sulphuric  acid,  and  7  pounds  of  water.  We  killed  moths  and  their  eggs,  worms  and 
bugs  of  all  kinds,  wasps,  mud-daubers,  spiders,  bats,  rats,  and  mice,  and  also  English 
sparrows  perched  outside  on  the  roof.  It  has  just  been  one  month  since  we  fumigated, 
and  we  see  no  more  as  yet.  There  is  no  sense  in  a  miller  being  pestered  with  the 
flour  moth.     Hydrocyanic-acid  gas  will  kill  the  moth  and  the  eggB. 

Our  correspondents  also  wrote  that  in  their  opinion  it  would  be 
difficult  to  operate  any  mill  infested  with  the  flour  moth  without 

a  Ninth  Annual  Report  State  Entomologist  of  Minnesota,  pp.  31-36,  1904;  Special 
Report  State  Entomologist  of  Minnesota,  February  29,  1904. 
[Clr.  112] 


fumigation,  as  the  cos1  of  shutting  down,  cleaning  machinery,  etc., 
would  destroj  the  profit.  In  this  latter  fumigation,  54  pounds 
oyanid  of  potash  were  used,  equivalent  t"  13.9  ounces  to  1,000  cubic 
feet,  or  aboul  one-third  more  than  necessary  if  the  building  was  tight 
and  the  ingredients  known  to  be  pure. 

BUHMAR1    OF    VALUE    <>i      nil.    HYDROOTANIO-AOID    OAfl    METHOD. 

The  special  qualities  of  hydrocyanic-acid  <;ns  and  some  of  the  ad- 
vantages  which  it  possesses  over  other  insecticides  (as  well  as  it- 
disadvantages)  as  q  fumigant  for  mills  and  other  buildings  infested 
by  insects  may  be  briefly  summarized  as  follows: 

1.  It  is  generated  without  the  aid  of  fire,  in  which  respect  there 
i-  a  distinct  advantage  in  its  use  in  preference  to  sulphur  fumiga- 
tion, utiles  the  Clayton  process  i-  employed. 

2.  It  is  practically  noninflammable   and   nonexplosive  in  a  large 

confined  -pace  when  generated  according  to  methods  now  in  practice. 

.;.  It  i-  possible,  therefore,  to  use  this  method  of  fumigation  when' 
with  the  employment  of  cither  bisulphid  of  carhon  or  Bulphur  a  con- 
tlict  with  insurance  companies  might  occur. 

I  It  is  not,  injurious  to  cereals  or  other  dried  products  in  storage, 
either  for  food  or  for  seed,  in  which  respect  it  i-  superior  to  sulphur, 
which  destroys  the  germinating  qualities  of  seeds  as  well  as  plant 
life  generally. 

").  Fumigation  may  he  employed  at  any  time,  night  or  day,  but 
preferably  in  a  moderately  warm  temperature  and  on  a  calm  day 
w  ithout  wind. 

6.  In  a  very  short  time  after  ventilation  of  the  treated  premises 
the  characteristic  "peach-pit"  odor  of  the  gas  entirely  disappears 
and,  properly  used,  no  -olid  residue  remains  in  the  generator. 

7.  Hydrocyanic-acid  gas  is  lighter  than  air  and  ha-  considerable 
penetrating  power — not  so  great,  however,  a-  possessed  by  sulphur 
where  forced  into  buildings  and  other  inclosures  by  means  of  the 
Clayton  pro.  i 

-  The  gas,  generated  in  air-tight  inclosures,  creates  a  positively 
deadly  atmosphere,  and  thus  used  destroys  most  Btages  of  the  Hour 
moth   and   some   other   insects.      It    i-   still    more   deadly  at    a   much 

shorter  exposure  to  man  and  other  mammals,  including  domestic 

animals,  rats,  mice,  and  other  vermin,  than  to  mill  insects. 

9.  It  is  tin1  mosl  powerful  poison  in  common  use,  which  fact  being 
fully  recognized,  human  beings  are  not  readily  tempted  to  run  unnec- 

ri>ks  of  exposure  to  its  deadly  fumes. 

10.  The  pre  -  comparatively  inexpensive  under  conditions 
which  permit  of  buildings  being  made  nearly  gastight,  especially 
when  a  complete  exposure  of  between  l'4  and  36  hour-  can  he 
obtained. 

[Or.  112] 


CIIEMICALS    AND    OTHER    SUPPLIES. 


In  the  fumigation  of  mills,  warehouses,  elevators,  and  other  struc- 
tures and  inclosures  infested  by  insects,  especially  the  Mediterranean 
Hour  moth  and  some  other  soft-bodied  insects,  in  stored  cereals,  with 
hydrocyanic-acid  gas  two  chemicals  are  used,  both  poisonous  and 
dangerous  to  handle.  They  are  cyanid  of  potassium,  called  also 
potassium  cyanid  and  cyanid  of  potash,  of  a  high  grade  or  chemically 
pure  (98-99  per  cent),  concentrated  sulphuric  acid  having  a  specific 
gravity  of  about  1.83  or  1.84  (equivalent  to  66°Baume),  and  water. 
The  standard  commercial  sulphuric  acid  will  answer. 

Cyanid  of  potash  (KCN  or  KCy),  the  first  ingredient,  is  a  white 
crystalline  salt,  permanent  in  dry  air,  but  rapidly  decomposable  or 
deliquescent  in  a  moist  atmosphere,  when  it  gives  off  an  odor  of 
hydrocyanic  or  prussic  acid.  It  is  readily  soluble  in  water,  has  a 
bitter  taste,  and  is  extremely  poisdnous. 

Sulphuric  acid  (H2S04),  the  chemical  used  in  liberating  the  gas,  is 
so  well  known  as  scarcely  to  require  description  at  this  point.  It 
might  be  well,  however,  to  state  that  it  is  known  commercially  also 
as  oil  of  vitriol  or  simply  "vitriol,"  and  is  a  dense,  oily-looking  fluid, 
colorless  when  pure,  having  when  concentrated  a  specific  gravity  of 
about  1.8,  and  containing  about  90  per  cent  H2S04.  It  is  nearly 
twice  as  heavy  as  water,  and  in  action  it  is  powerful,  being  corrosive 
to  both  animal  and  vegetable  substances. 

Hydrocyanic  acid  (HCN  or  HCy),  the  resultant  gas  liberated  by 
combining  cyanid  of  potash  and  sulphuric  acid,  is  one  of  the  most 
energetic  poisons  known  to  science.  A  single  drop  of  the  pure  acid 
placed  inside  of  the  eye  causes  instant  death.  When  taken  internally 
it  causes  paralysis  of  the  heart,  of  the  respiratory  center,  and  of  the 
vasomotor  region  of  the  medulla.  The  immediate  cause  of  death  in 
most  cases  is  due  to  obstruction  of  the  respiration  or  to  stoppage  of 
the  heart's  action. 

The  purity  of  the  cyanid  of  potash  and  sulphuric  acid  to  the 
degree  indicated  above  is  essential  to  the  success  of  fumigation, 
and  efforts  should  be  made  to  obtain  these  chemicals  through  thor- 
oughly reliable  firms,  and  if  there  is  any  doubt  as  to  their  strength 
they  should  be  submitted  to  analysis.  Many  of  the  disappointments 
and  failures  in  fumigation  have  come  from  the  employment  of  impure 
cyanid  of  potash  or  acid  below  the  standard  strength.  These  two 
agents  are,  however,  now  in  such  common  use  for  fumigation  pur- 
poses that  with  ordinary  care  in  their  purchase  there  is  little  risk  in 
this  direction. 

|Cir.  Ill'] 


PR(  IPOR1  l«'\    <>i     (  IIEMII    \l  3. 

The  hydrocyanic-acid  gas  is  produced  l>y  a  combination  of  cyanic] 
of  potash  ami  sulphuric  acid  in  water.  The  most  economical  and 
efficient  production  of  the  gas,  as  demonstrated  by  a  recent  thorough 
investigation  of  the  subject  by  the  Bureau  of  Entomology  in  coopera- 
tion with  tin1  Bureau  of  Chemistry  of  the  Department  of  Agriculture, 
is  obtained  l>\  the  following  proportions: a 

<  !yanid  of  potash  (98  percent  pure),  by  weighl ...   I  ounce  avoirdupois. 

Commercial  sulphuric  acid,  by  measure I  fluid  ounce. 

Water,  by  measure :i  fluid  ounces. 

This  formula  differs  somewhat  from  -nine  other  formulas  in  use 
in  mill  fumigation.6  Any  combination  of  the  three  ingredients  will 
produce  gas,  and  hence  any  one  of  several  formulas  which  have  been 
recommended  and  are  in  use  will  yield  more  or  Less  satisfactory 
results,  hut  the  greatest  economy  in  materials  with  a  maximum  gas 
production  i-  secured  by  following  the  above  proportions.  In  this 
formula  the  acid  and  water  are  slightly  in  excess  <'f  the  exact  chemical 
need-,  hut  it  i-  essential  that  all  the  eyanid  shall  he  converted  ajid 
that  there  he  sufficient  water  present  to  maintain  a  completely 
liquid  residue.  The  use  of  less  water,  e.  i_r.,  two  parts,  may  cause  a 
-olid  residue,  due  to  undissolved  potassium  sulphate,  the  by-product 
resulting  from  the  reaction  by  which  hydrocyanic-acid  gas  i-  produced, 

R  8.  Woglum,  Hul  No.  :•>.  Bur.  Ent.,  U.  S  Dept.  Alt.,  p. :):',,  Juno  11,  1909. 
''The  formula  1 1 :  1:3)  above  quoted  may  look  quite  distinct  from  older  ones  which 
have  been  in  Bomewhat  general  use  by  millers,  rumigators,  and  others,  hut  the  differ- 
ence i-  v.ry  slight  and  may  be  explained.  The  old  formula,  a.-  originally  advised 
by  Johnson  Fumigation  Methods,  1902,  p.  163  <.  read-  substantially  that  to  determine 
the  amount  <>f  acid  and  water  one-half  more  acid  (liquid  measure)  than  eyanid  and 
■  ■lie  half  more  water  than  and  are  used.  Therefore  a  room  _'0  by  30  by  10  feet 
require-  :..!  ounces,  by  weight,  ot  eyanid;  80  ounce-,  liquid  measure,  sulphuric  acid, 
and  120  ounces,  liquid  measure,  water."  as  originally  advised  by  Johnson,  the 
sulphuric  acid  was  liquid  measure,  hut  later  a  more  effective  formula  for  fumigating 
mill-*  and  similar  inclosures  came  Into  use,  giving  the  acid  by  weight.  A  formula 
substantially  as  follows  was  substituted  with  hotter  result.-*: 

mid  of  potash   98  per  cent  pure  .  by  weight . .   1  ounce  avoirdupois. 
Commercial  sulphuric  acid  (93  per  cent  pun 

by  weighl 1}  ounces  avoirdupois. 

Water    .  _'J     fluid     ounces     <>r 

ounce-,  avoirdupois. 
In  |M.int  of  fact,  the  formula  last  quoted  substitutes  the  computation  of  the  acid  hv 
lit  for  computation  bj   measure  as  used  in  earlier  formula-     Thus,  while  the 
avoirdupois  formula  remain-  nearly  the  same,  owing  to  the  greater  atomic  weight  of 

the  acid,  the  chemical  reaction  i-  almost  identical  with  the  formula   I:  1  : :'.,  which  we 
now  ad>  i 

Theoretically  the  difference  in  acid  between  the  two  formulas  i-  BO  slight  that  in 
fumigating  mills  the  results  are  about  equal.     In  some  cases  there  mighl  he  a  Blight 
1  deficiency,  resulting  in  a  proportionate  d<  Bciency  in  the  amount  of  l*.i-  evolved. 
795    I  ii    i  12     10 


10 

and  this  solidifying  or  "freezing"  of  the  residue  may  prevent  com- 
plete development  of  the  gas,  as  has  been  demonstrated. 

Much  recent  work  by  experts  and  agents  of  this  Bureau  has  dem- 
onstrated that  for  ordinary  well-constructed  mills  or  granaries  good 
results  may  be  anticipated  by  the  use  of  10  ounces  of  cyanid  of  pot- 
ash and  corresponding  amounts  of  the  other  ingredients  to  1,000 
cubic  feet  of  air  space.  This  strength,  therefore,  may  be  taken  as 
the  standard  for  mill  and  granary  fumigation. 

If  mills  could  be  made  practically  air-tight,  and  some  are  nearly 
so,  undoubtedly  a  considerably  smaller  amount  of  cyanid  to  each 
1,000  cubic  feet  would  give  equally  good  results,0  but  the  miller  will 
hardly  be  willing  to  risk  success  by  a  slight  economy  in  cyanid  and 
acid,  in  view  of  the  money  loss  due  to  "shut  downs"  incidental  to 
any  fumigation. 

In  very  loosely  constructed  or  more  or  less  open  frame  buildings, 
or  where  only  a  short  exposure  is  permissible,  it  is  practically  impos- 
sible to  successfully  fumigate  for  most  insects  affecting  stored  prod- 
ucts; but  sometimes,  by  increasing  the  amount  of  cyanid  to  double 
the  quantity  normally  employed,  fair  results  may  be  obtained. 

Good  results  can  not  be  expected  with  an  exposure  of  less  than 
16  or  18  hours,  while  a  period  of  from  24  to  36  hours  is  preferable. 

ESTIMATING    AMOUNTS    OF   CHEMICALS    FOR    FUMIGATION    OF   MILLS. 

The  first  preliminary  to  the  fumigation  of  a  mill  or  granary  is  the 
making  of  an  accurate  estimate  of  the  amount  of  chemicals  required 
for  the  different  stories  of  the  building.  It  is  desirable  to  make  the 
computation  of  space  for  each  floor  separately  and  to  prepare  a  table 
for  the  guidance  of  the  operators  indicating  the  number  of  generators 
and  the  amount  of  chemicals  to  be  distributed  on  each  floor.  Inside 
measurements  should  be  taken,  and  the  height  of  each  stoiy  should 
be  carefully  measured  as  well  as  the  floor  space. 

Under  ordinary  conditions  it  is  best  to  generate  the  gas  at  the 
standard  rate  on  each  floor  of  the  building.  The  first  table  which 
follows  illustrates  the  normal  proportions  for  each  floor.  These 
tables  are  submitted  as  indications  of  a  convenient  method  to  be 
followed  in  making  the  computations  and  tabular  statement.  In 
view  of  the  fact,  however,  that  the  gas  is  lighter  than  air  and  rises, 
it  may  be  desirable  in  the  case  of  buildings  which  have  many  open- 
ings from  one  floor  to  another,  which  can  not  be  easily  sealed  or 
stopped  up,  to  develop  the  greatest  amount  of  gas  in  the  basement. 

a  Mr.  C.  H.  Popenoe,  working  under  the  instructions  of  the  writer  in  the  vicinity 
of  the  District  of  Columbia,  and  Mr.  D.  K.  McMillan,  fumigating  under  the  writ 
directions  in  Kansas,  have  met  with  success  with  lower  strengths  in  fumigating  nearly 
air-tight  mills  and  other  structures. 
[Cir.  112] 


and  n  decreasing  amount  on  each  of  the  succeeding  floors,  maintain 
ing  the  total  proportion  for  the  building,  however,  at  approximate^ 
1 0  ounces  of  cyanid  to  1 ,000  cubic  feet  of  space,      ^n  estimate  of  this 
kind  is  illustrated  l>\   the  second  table. 

Assuming  thai  the  capacity  of  the  upper  floor  of  a  given  building 
16,000  cubic  feet,  tin-  minimum  amounts  of  each  reagent  and  wafer 
required,  according  to  the  same  formula,  would* be" 

'  'van ill  of  potash  80  pounds  avoirdti] 

Sulphuric  acid  •  •<>  pint* 

Water 180  pints 

This  would  necessitat  •  the  use  of  twentj  3-gallon  generators  and 
would  naturally  require  the  same  number  of  l>a:_r-  which  would  con- 
tain 3  pound-  e'ach  of  the  cyanid  ^alt. 

While  it  i-  essential  to  success  that  the  cubic  contents  of  each  floor 
be  accurately  computed,  it  can  be  readily  seen  from  the  foregoing 
that  many  of  the  details  as  to  the  strength  must  be  left  to  the  ju< 
ment  of  the  operator,  since  we  have  reports  of  nonsuccess  or  of  only 
partial  success  where  greater  strengths  have  been  used.  As  fre- 
quently happens  these  reports  emanate  from  distant  sources  and  it 
has  not  been  possible  to  give  them  personal  investigation." 

Whenever  a  building  can  not  be  so  t  iirht  |y  closed  as  in  t  he  case  last 
mentioned  and  this  matter  must  necessarilj  he  left  to  the  judg- 
ment of  the  operator  additional  quantities  are  necessary.  This  - 
accomplished  by  employing,  tor  each  1,000  cubic  feet,  one-fourth  to 
one-half  more  or  even  twice  the  quantity  of  each  ingredient.  The 
amounts  to  be  used  for  other  still  more  loosely  constructed  buildings 
can  be  calculated  in  the  same  manner. 

The  following  tabular  statements  are  submitted  as  aids  in  com- 
puting the  exact  proportions  for  hypothetical  buildings  of  about  1,000 
hands  (dail)  I  capacity  , 

The  amount-  of  chemicals  to  be  used  for  a  given  building  or  other 
inclosure  are  in  direct  proportion  to  the  degree  of  tightness  to  which 
it  may  be  closed.  Owing  to  the  great  variability  of  buildings  and 
part-  thereof  as  regards  tightness,  it  follow-  that  no  uniform  strength 
can  he  prescribed. 

an  example,  a  Wisconsin  miller  wrote  in  June,  1909,  that,  although  he  had  used 
hydrocyanic-acid  gae  at  the  rate  oi  2  oun<  es  of  cyanid  '"  eai  h  100 

1,000  cubic  fe<  !••«  individual*  to  have  been 

missed  although  everything  within  reach  of  tin-  gae  was  positively  killed.    This  led 
t"  the  conclusion,  in  which  1 1 1  < >— i  millers  of  experience  concur,  that  l  re  seldom 

killed  by  thi<  or  other  methods  "i  fumigation  now  in  use,     Professor  Washburn,  how- 
ever, has  succeeded  in  destroying  them,  and  we  fumigated  1 1 
mill  product  in  which  there  \\  ies  which  later  failed  '"  devi 

h  It  should  ln>  here  stated  that  miller-  generally  ate  very  apt  to  take  the  outside 
measurements  of  a  building  instead  of  the  inside  and  do  not  always  calculate  with 
sufficient  care  the  heighl  oi  each  t' 
fCir.  112] 


L2 

Tables  designating  dimensions  and  cubic  contents  of  each  floor  and  amount  of  chemicals. 

TEN-OUNCE   TABLE. 


Floor. 


Dimensions. 


Cubic 

feet. 


Cyanid.       Acid.        Water.     ^entr- 
ators. 


Basement 40x60x10  24.000 

First  lloor * 40  x  Ml  x  Is  13,200 

Second  lloor 40  x  Ml  x  1 1  33,600 

Third  floor 40x60x12  28,800 

Fourth  lloor 40  x  60  x  Is  43,200 

Total  a : 172  900 


108 


ins 


Pounds. 

Pints. 

Pints. 

15 

15 

4.", 

>- 

27 

si 

21 

21 

63 

Is 

18 

54 

27 

27 

81 

324 


a  Assuming  the  oosl  of  cyanid  of  potash  at  25  cents  a  pound,  this  would  brine  the  sum  for  the  most 
expensive  chemical  to  $27.  Calculating  the  sulphuric  acid  at  3  cents  a  pound  (1  pint=  1.84  pounds) 
the  cost  would  be  $5.96  or  $32.96  as  the  total  cost  of  the  chemicals. 


Table  for  mills  with  openings  in  floors. 


Floor. 

Dimensions.       ffpt!j'1        Cyanid. 

Acid.        Water. 

ators. 

Basement 

First  floor 

40  x  60  x  10          24,000                 36 
40  x  HO  x  Is          43,200 

36              108 
36                10* 

12 
12 

Second  floor. . . 

40  x  60  x  14          33,600                 24                 24                 72 
40  x  60  x  12         28,800                12                12                36 

40  x  00  x  Is          43. 200                   0 

s 

Third  floor 

4 

Fourth  floor 

0 

This  table  Is  intended  for  use  in  buildings  having  large  openings,  as  belt  holes,  freight  elevator  shafts, 
and  open  stairways  in  the  floors,  serving  to  throw  the  whole  building  into  one  large  room. 

PREPARING    THE    MILL    OR    OTHER    BUILDING    FOR    FUMIGATION. 


After  obtaining  the  chemicals  for  generating  the  gas  the  building 

should  be  made  as  nearly  gas-tight  as  possible,  since  upon  this  feature 
alone  depends  the  amount  of  chemicals  to  be  used.  If  the  building 
could  be  made  approximately  air-tight,  the  amount  could  be  mate- 
rially reduced  "with  consequent  saving  of  expense. 

To  compass  the  object  desired,  every  window  must  be  closed  as 
tightly  as  possible.  A  good  -way  is  to  insert  plugs  of  wood  on  each 
side  of  the  top  of  the  lower  sash  and  between  the  "strip."  If  this 
does  not  make  the  aperture  between  the  two  window  sashes  tight 
enough,  other  substances  may  be  used.  Cotton  batting  of  good 
quality  is  serviceable  for  inserting  into  these  openings  with  a  case 
knife,  care  being  taken  that  it  is  packed  tightly  and  not  loosely.  A 
cheap  grade  of  batting  can  be  used  for  stopping  other  aperture-. 
Toweling  or  rags  may  be  substituted,  and  after  being  placed  under 
running  water  can  be  dried  and  reused.  Macerated  newspapers 
might  serve  the  purpose,  but  perhaps  the  best,  because  the  most 
secure,  remedy  for  general  use  consists  in  pasting  paper  over  the 
aperture,  uncalendered  paper  of  the  quality  of  cheap  w  all  paper  or 
any  comparatively  porous  but  not  pulpy  paper  being  serviceable. 
Newspapers  are  apt  to  be  too  soft  for  this  purpose.  Cracked  panes 
should    be   replaced,   or  paper  may   be   pasted  over   the   apertures. 

[Cir.  112  J 


13 

Similar  treatment  should  be  gives  i"  the  doors  and  all  other  natural 
outlets,  including  the  chimneys,  fireplaces,  flues,  registers,  ventilators, 
cracks  in  the  ceilings  and  walls,  and  accidental  apertures,  such  a-  rat 
holes  in  the  floor.     All  of  these  should  be  tight!}  closed. 

li  is  always  advisable  that  at  least  two  persons  be  present  for  a  last 
inspection  before  the  final  work  of  liberating  the  l,m-.  Even  aftei  all 
preparations  are  made  an  outlet  may  sometimes  be  discovered  that 
has  escaped  not  ice. 

To  provide  for  quick  and  thorough  ventilation  after  the  process  is 
completed  two  or  more  opposite  windows  should  be  left  unlocked  and 
arranged,  especially  in  the  upper  floors,  so  that  they  may  be  pulled 
down  or  up,  as  the  case  may  be,  by  means  of  a  muii!  cord  or  rope  fron 
the  outside." 

t  i.i.  \\t\«,    i  in:    MILL. 

\-  an  initial  step  to  the  fumigation  of  a  mill  or  other  structure 
inhabited  by  the  flour  moth,  it  is  important  to  clean  it  as  thoroughly 
as  possible  and  remove  all  infested  Hour  or  other  mill  product  and 
promptly  burn  it.  that  as  many  of  the  caterpillars,  pupa\  and  eggs 
of  the  insect  a--  possible  may  he  destroyed.  Most  progressive  miller- 
employ  a  system  of  cleaning  out  before  fumigating,  since  before  the 
genera]  adoption  of  fumigation  methods  in  our  principal  milling  cen- 
ters the  only  recourse  was  to  close  down  the  mills  (which  it  was 
found  necessary  in  .some  cases  i"  do  a-  often  as  twice  a  week)  and 
clean  out  everything  by  mechanical  mean-.  It  i-  feared,  however, 
that  too  often  the  sweepings  are  not  properly  disposed  of  by  prompt 
burning. 

The  operation  includes  the  cleaning  of  all  spouts,  elevator  legs, 
purifiers,  and  other  part-  of  the  machinery  and  other  equipment,  as 
also  the  wall-,  ceilings,  corner-  in  fact,  every  portion  of  the  building 
in  which  the  insect  could  find  lodgment.  The  reason  for  cleaning 
out  at  tin-  time  is  to  afford  the  gas  a  better  chance  to  penetrate  all 
parts  of  the  building  so  as  to  kill  the  insects  in  their  various  -taire- 
Every  particle  of  infested  flour  and  w  aste  material  w  Inch  might  harboi 
the  insect  or  its  eggs  should  he  swept  down  and  out  until  the  mill 
appears  t<>  he  absolutely  clean.  Then  a-  soon  as  possible  thereaftei 
the  preliminaries  of  the  actual  fumigation  should  he  undertaken. 

Elevator  and  hilt  brush.  For  cleaning  elevators  infested  by  the 
Mediterranean  flour  moth.  Johnson  long  jilt"  advised  a  brush  similar 
to  the  one  illustrated  (fig.  f '.  It  is  made  by  taking  a  piece  of  1  I -inch 
hoard  of  the  same  dimensions  as  the  elevator  cups,  fastening  the 
hrist  les  to  three  sides.     Side  A  is  fastened  to  the  elevator  belt  with  flat- 


•The  details  of  arrangement*  are  considered  in  »  in  ulare  t  i li i - 

Bureau,  which  are  i  »r  gratuitous  distribution. 

Hir.  UJl 


14 

headed  bolts  running  through  the  board,  as  shown  at  BB,  the  bolts 
being  1-inch  or  |-inch.  The  bristles  on  the  sides  CC  should  be  |-inch 
long,  but  those  at  1)  should  be  longer,  so  that  a  good  brushing  to  the 

outer  side  of  the  elevator  may  be  secured.  Such  a  brush  can  be  made 
to  lit  any  size  of  elevator.  As  it  has  been  in  use  for  manv  veal's 
and  is  still  advised  by  the  American  Miller  to  correspondents,  it  is 
necessarily  of  value,  and  something  similar  should  be  used  in  every 
mill. 

( leaning  by  suction. — For  a  long  time  the  writer  has  been  endeavor- 
ing to  ascertain  if  millers  have  tried  the  system  of  vacuum  cleaning 
advertised  in  our  monthly  magazines,  and  has  just  received  word  from 
one  of  these  companies  to  the  effect  that  it  has  only  recently  taken  up 

flour-mill  work.  The  com- 
pany, however,  is  satisfied, 
beyond  any  question  of  a 
doubt,  that  their  system 
will  clean  a  flour  mill  more 
cheaply  than  can  be  done 
by  any  other  process.  Con- 
siderable experiment  al 
work  is  being  done  in  some 
of  the  principal  mills  ;it 
Minneapolis,  and  in  one  of 
these  a  plant  was  installed 
some  time  ago.  The  diffi- 
culty in  this  case  is  that 
the  steam  pressure  is  not 
sufficient  to  work  one  of  the 
aspirator  systems,  and  this 
matter  is  now  being  inves- 
tigated with  a  view  to  changing  the  plant  to  another  mill  where  suit- 
able conditions  can  be  obtained. 


Fig.  4. 


Elevator    and    belt   brush,  for  cleaning  elevators 
infested  by  the  Mediterranean  Hour  moth. 


METHOD    OF    'STRINGING       A    BUILDING    FOR    FUMIGATION. 

While  the  "stringing"'  method  of  fumigating  mills  and  other  large 
buildings  is  scarcely  necessary,  there  are  some  persons  who  may  \\  ish 
information  in  regard  to  it.  The  strings  are  arranged  so  as  to  hang 
directly  over  each  generator,  and  are  carried  through  screw  eyes  in 
the  ceiling  or  woodwork  to  doors  or  stairways  leading  out  of  the 
room  to  be  treated.  The  screw  eyes  should  be  firmly  secured,  and 
the  best  quality  of  cord  of  the  proper  size  should  be  employed. 
The  bags  containing  the  cyanid  of  potash  are  suspended  directly 
over  the  vessels,  preferably  after  the  acid  is  added  to  the  water  in  the 
[Cir.  mj 


L5 

jui,  care  being  taken  thai  there  is  no  danger  of  their  dropping  into 
the  generator  prematurely.  A  small  wire  hook  attached  t"  th< 
of  each  cord  can  be  used,  but  if  the  string  is  tied  firml)  around  the 
neck  of  the  sack  it  causes  less  trouble  and  is  quite  as  Becure.  The 
cords  ni:i\  be  so  arranged  that  the  cyanid  can  all  be  lowered  into 
the  jars  bj  one  motion.  The  entire  process  is  well  shown  l»\  the 
accompany  ing  illustration  I 

A  mure  detailed  description  of  the  "stringing"  process,  bj  which 
many  l>aur>  of  cyanid  may  be  lowered  into  the  generators,  would 
require  too  much  -pace  for  treatment  here.  The  operator,  if  he 
chooses  this  method,  may  use  his  own  device-.     Pulleys  and  screw 


Pre.  5     M  •  aging  .1  rooi 

eyes  are  practically  necessary  in  the  application  of  the  "stringing'' 
method. 

The  method  is  much  used  in  greenhouse  work  and  is  desirable  for 
small  buildings.  This  process  of  "stringing"  the  building  would 
scarcely  he  found  profitable  for  mills  or  dwellings,  hut  in  greenhouse 
work  fumigation  is  frequently  done  every  week  or  two  and  often 
several  times  a  week,  and  the  equipment  of  screw  eyes,  pulleys,  etc., 
can  remain  in  place  almost  indefinitely. 

as  should  he  placed  on  the  doors  of  the  building  that  is  being 
fumigated,   warning   passers-by   of   the   danger,   e.    g.,   "Danger!" 
"Hydrocyanic-acid  gas!"  "Poison!"     The  building  must,  of  cot: 
he  vacated  and  neighbors  warned  of  the  nature  of  the  operation. 

[Clr.  u-l 


16 

Frequently  these  precautions  are  not  observed,  and  although  no 
casualties  arc  on  record  it  is  the  part  of  wisdom  always  to  be  on  the 
sale  side. 

PROCESS    OF    FUMIGATION". 

Tn  the  process  of  generating  the  gas  the  water  is  usually  measured 
in  a  glass  beaker  indicating  ounces,  and  poured  into  an  earthenware 
crock  or  generator.  To  this  is  added  the  acid,  measured  in  the  same 
beaker,  which  is  slowly  and  gently  poured  into  the  water  to  avoid 
splashing  or  boiling.  The  acid  should  never  be  placed  in  the  genera- 
tors-first, as  advised  by  some  writers,  since  experience  shows  that 
this  is  dangerous,  spattering  being  almost  certain  to  follow.  When 
the  acid  is  poured  into  the  water  in  the  jar  an  ebullition  of  vapor 
sometimes  arises. 

When  the  cyanid  of  potash  is  finally  dropped  into  the  combined 
acid  and  water  mixture  an  ebullition  or  bubbling  also  takes  place 
similar  to  that  which  is  produced  by  a  red-hot  iron  dipped  into  cold 
water.  Next  is  given  off  the  hydrocyanic-acid  gas,  the  most  poi- 
sonous gas  in  common  use.  It  is  colorless  and  has  an  odor  which  is 
likened  to  that  of  peach  kernels."  If  the  fumes  are  inhaled  they  are 
almost  certain  to  prove  fatal;  hence  the  necessity  of  extreme  care 
and  the  advisability  of  two  intelligent  operators  in  this  work.  It  is 
even  advisable,  especially  when  the  first  fumigation  is  undertaken, 
that  one  Avho  has  had  experience  with  this  method  of  fumigation  be 
present  to  give  directions.  The  odor  is  decidedly  metallic,  like  that 
produced  by  striking  two  pieces  of  metal  together,  or  of  metal  against 
stone. 

In  preparing  cyanid  of  potash  for  use  it  should  be  broken  into 
lumps  about  the  size  of  an  egg  or  a  little  smaller,  by  pounding  it  on 
a  stone  in  the  open.  The  cyanid  should  never  be  broken  in  the 
hands  nor  should  it  be  handled  without  rubber  or  leather  gloves. 
The  smaller  fragments,  if  not  too  many,  are  serviceable  when  equally 
apportioned  as  regards  large  and  small  particles,  and  weighed  out 
in  3-pound  lots  and  placed  in  paper  bags  or  sacks. 

The  bags  should  be  of  moderately  thin  paper,  because  if  as  thin  as 
tissue  the  action  of  the  acid  might  be  so  rapid  as  to  constitute  an  ele- 
ment of  danger.  If  too  thick,  action  would  be  delayed  or  checked, 
which  would  militate  against  the  desired  results.  Before  use,  the  bags 
should  be  placed  in  a  can  and  kept  free  from  moisture,  which  the 
cyanid  salt  is  apt  to  absorb  from  the  air,  affording  opportunity 
for  leakage  through  the  bag.  In  some  cases,  to  avoid  this  leakage, 
two  thin  bags,  one  within  the  other,  might  be  necessary.  Washburn 
experimented  in  the  use  of  two  sacks  with  the  result  that  at  least 
20  seconds  elapsed  before  the  gas  was  evolved. 

"The  writer  fails  to  detect  the  resemblance. 
[Cir.  112] 


17 

As  soon  ns  nil  preliminaries  have  been  arranged  and  the  acid 
has  been  added  to  the  water  in  the  generators,  a  bag  containing  the 
cyanid  should  be  left  at  the  aide  of  each  generator. 

After  seeing  thai  the  generators  are  placed  in  rows  so  as  to  afford 
opportunity  for  rapid  action  and  the  acid  has  been  added  to  the 
\\;iicr  in  each  "l"  the  jars,  begin  operations  in  the  upper  floor  of  the 
building  mid  place  the  cyanid  gentlj  in  each  jar,  passing  from  one 
jar  to  another  as  quicklj  as  possible  and  as  quickly  leaving  the  room, 
going  downward  to  the  next  Hour,  where  the  process  is  repeated  until 
the  last  floor  or  basemenl  is  reached,  where  exil  is  made.  The  outer 
doors  should  l>e  locked  and  a  watchman  stationed  outside  until  the 
process  is  completed. 

This  process  ma\  be  varied  if  strings  or  stoul  cords  are  used  for 
lowering  the  hairs  of  cyanid  into  the  jars  from  the  outside,  as  pre- 
viously described. 

A  -till  (lav  should  be  selected  for  fumigation.  In  case  "f  a  high 
wind  the  funics  of  the  gas  will  escape  strongly,  which  will  not  alone 
interfere  with  the  success  of  the  fumigation,  hut  ma\  cause  alarm 
to  neighbors  should  the  building  not  he  an  isolated  one. 

Better  results  are  claimed  for  a  warm  temperature,  saj  70  F, 
or  above,  than  in  a  temperature  as  low-  as  50  K.  or  below.  Under 
on  most  insects  become  torpid  and  the  effective  action  of  the  chemical 
will  he  diminished,  especially  in  very  low  temperature-. 

The  best  time  that  could  he  chosen,  ami  which  i-  generally  used 
where  circumstances  permit,  is  during  daylight  on  a  Saturday  after- 
noon or  very  early  Sunday  morning.  This  gives  a  longer  exposure 
than  can  usually  be  obtained  unless  a  day  preceding  a  holiday,  when 
all  mill  hands  are  on  vacation,  may  be  chosen.  This  permits  of  a 
full  exposure,  as  in  many  cases  it  removes  the  necessity  of  ventilating 
the  building  until  early  the  following  Monday  morning. 

A  single  fumigation  will  in  most  cases  destroy  all  hut  a  few  indi- 
vidual insects,  especially  if  conditions  are  favorable.  As  a  rule,  how- 
ever, it  is  only  a  matter  of  a  few  days  or  week--  before  the  moths  may 
he  seen  beginning  to  By  about  the  building  or  resting  on  the  walls 
and  machinery.  To  guard  againsl  reinfestation,  therefore,  a  second 
treatment  must  he  given,  at  the  end  of  the  third  to  the  fourth  week. 
according  to  the  number  of  moth-  w  bich  may  have  issued  in  the  mean- 
time. If  after  the  expiration  of  another  interval  the  insects  are  still 
present  a  third  fumigation  may  he  accessary.  A  third  treatment  i- 
not  usually  required,  however. 

Most    millers   who   practice    this    method    of   fumigating   employ    it 

once  a  year,  some  at  the  intervals  above  stated,  others  at  intervals 
of  six  months.  One  Michigan  miller  claims  that  in  hi-  case  after  one 
thorough  fumigation  it  is  unnecessary  to  repeat  the  process  until 
two  years  have  elapsed. 

I  fir.  112] 


18 

The  cans  or  other  receptacles  containing  the  cyanid  of  potash 
should  be  plainly  labeled  "Poison!"  and  each  operator  should 
become  thoroughly  familiar  with  the  dangers  which  may  attend  a 
failure  to  carry  out  directions  explicitly. 

POSSIBLE    DANGERS    IN    USE. 

As  soon  as  the  bag  containing  the  cyanid  is  dropped  into  the 
generator  the  operator  passes  quickly  to  the  next  generator,  and  so 
on.  It  is  not  safe  to  linger  under  any  circumstances  or  to  return  in 
case  of  any  omission.  Any  deviation  from  the  set  rules  may  mean 
the  loss  of  life. 

The  residue  in  the  fumigating  generator  after  the  operation  is 
completed  consists  of  sulphate  of  potash,  sulphuric  acid,  and  water. 
Sometimes  if  the  chemicals  are  not  of  the  proper  strength  or  are  not 
properly  combined  a  certain  amount  of  cyanid  of  potash  remains  and 
hydrocyanic-acid  gas  is  given  off.  This  residue  is  an  element  of 
danger  and  should  not  be  left  in  the  generators  after  use,  but  promptly 
poured  or  thrown  into  a  sewer  trap  or  buried.  The  generator  should 
then  be  thoroughly  cleaned  in  running  water. 

A  question  often  asked  by  persons  contemplating  the  employment 
of  the  hydrocyanic-acid  gas  method  of  treating  buildings  is  as  to 
whether  it  is  dangerous  to  the  contents.  It  is  apt  to  tarnish,  though 
not  permanently,  polished  brass  and  nickel  when  exposed  to  its  action. 
Where  such  fittings  can  be  conveniently  removed  it  will  save  trouble, 
otherwise  they  may  be  treated  after  fumigation  as  if  tarnished 
through  any  other  cause.  Liquid  or  moist  food  materials,  such  as 
milk  or  meats,  are  apt  to  absorb  the  gas  and  should  therefore  be 
removed. 

It  is  not  positively  known  that  fires  are  an  element  of  danger,  but 
persons  experienced  with  this  process  are  united  in  the  opinion  that 
to  avoid  the  possibility  of  risks  all  fires,  gas  jets,  and  the  like  should 
be  turned  off.  There  is  a  possibility  of  explosion  when  a  gas  is  gen- 
erated in  a  tight  inclosure,  hence  the  precaution. 

GENERAL    CAUTIONS. 

After  what  has  been  said  of  the  deadly  nature  of  hydrocyanic-acid 
gas  it  should  be  added  that  there  is  really  no  danger  if  the  directions 
given  in  this  publication  are  carefully  carried  out  to  the  letter  ami 
the  vapor  is  not  inhaled.  Even  to  taste  the  salt  might  have  fatal 
results,  and  it  is  dangerous  to  inhale  much  gas,  as  this  might  cause 
asphyxiation  and  death.0    Undoubtedly  thousands  of  successful  funii- 

a  Scores  of  entomologists  and  others,  including  many  employees  of  the  Department 
of  Agriculture,  have  successfully  used  this  gas  for  fumigating  rooms  and  buildings. 
It  is  in  general  use  as  a  greenhouse  fumigant  and  fur  nursery  stock  and  the  names  of  a 
hundred  persons  could  be  mentioned  who  have  had  practical  experience  with  it. 
[Cir.  lli'l 


Ill 

gations  have  been  made  of  inclosuree  and  as  jret  no  fatalities  have 
resulted.  Yet  it  is  worth  remembering  thai  operators  after  making 
numbers  of  fumigations,  are  apt  to  become  careless,  a  tendency  which 
should  be  avoided. 

One  form  of  accidenl  sh6uld  be  mentioned,  however.  If  a  matting 
of  newspapers  or  similar  materia]  is  noi  placed  under  each  fumigating 
jar,  or  if  the  water  is  added  to  the  arid,  instead  of  the  reverse  as 
advised  in  this  publication,  the  acid  is  apt  to  run  over  the  generator 
and  injure  the  floor  or  splash  upon  the  clothing  01  even  the  hands  of 
the  operator."  Such  accidents  have  happened,  and  t<>  pn>\  ide  against 
this  contingency  a  bottle  of  dilute  ammonia  should  be  at  hand. 

If  care  is  observed  in  labeling  the  receptacles  containing  the 
chemicals,  if  the  operators  before  using  this  method  become  thor- 
oughly conversant  with  it,  and  if  signs  are  placed  <>n  the  doors  <>f  the 
buildings,  the  chances  of  accidenl  will  be  reduced  t"  a  minimum  if 
not  entirely  eliminated.  After  fumigation  holdings  should  never  be 
entered  until  at  least  a  half  hour  (an  hour  or  two  i-  safer)  has  elapsed 
after  the  doors  and  windows  have  been  opened  for  ventilation,  and 
under  no  consideration  should  an  operator  return  to  the  place  jusi 
vacated  when  the  operation  is  under  way. 

9TJMMAR1     nr    OPERATIONS    AN  D    I'IM.<    UJTIONS. 

1.  Use  pure  chemicals,  generators  as  prescribed,  and  paper-  bags 
of  proper  quality. 

2.  Make  every  portion  of  building  as  nearly  gastighl  as  possible. 
.">.  Make  first  fumigation  in  ounces  to  1,000  cubic  feet  of  -pace, 

unless  building  is  unusually  loose,  in  which  case  more  must  be  used. 
t.  Repeat  fumigation  at  end  of  three  or  four  weeks  if  moth-  begin 
flying  or  other  evidence  of  infestation  is  shown. 

5.  Measure  every  portion  of  building  carefully  for  calculation  ..f 
the  proportions  of  chemicals. 

6.  Operators  should  be  intelligent  and  reliable.  Any  bookkeeper 
can  readily  calculate  the  cubic  contents  and  proportions  of  chemicals 
to  use.     Careless  men  should  not  he  employed. 

7.  Precautions  should  he  made  lor  prompt  ventilation  from  with- 
out, after  fumigation. 

0 During  July,  1909,  a  Michigan  miller  reported  thai  while  u-ii. 
ators,  It  of  them  boiled  over,  the  c  intents  Boiling  the  tl. >■  >r  badly.    The  explanation 
in  this  ca.-e  was  twofold:  First,  the  cyanid  was  broken  into  too  small  lumps,  den  i 
u  about  the  sue  of  coffee  berries,  and  the  floors  on  which  the  boiling  over  was  » 
were  t ho  two  upper  ones,  while  no  accidenl  happened  in  the  basement.     This  hap- 
pened during  very  warm  weather,  the  top  floors  being  hot  while  the  basemenl 
naturally  cool.     The  miller  reported  the  boiling  over  as  foil  -       a  out  of  10  on 

the  third  floor,  5  out  of  10  en  the  second,  2  oul  of  9  on  the  iir-t.  none  in  the  basement. 

U'ir.  112] 


20 

8.  Danger  signs  should  be  placed  in  position  and  a  watchman  sta- 
tioned outside1  until  the  operation  is  concluded. 

9.  Before  fumigating  clean  out  the  mills  thoroughly  and  provide 
for  the  penetration  of  the  gas  to  every  portion  by  moving  bags, 
boxes,  etc. 

10.  Do  not  fumigate  in  a  high  wind  or  in  a  low  temperature. 
Between  0.r)°  and  85°  F.  should  produce  the  best  results. 

11.  Begin  operations  in  the  upper  floors  and  pass  quickly  down- 
ward, placing  the  cyanid  gently  in  each  jar. 

12.  Fumigate  preferably  on  a  Saturday  afternoon,  lock  the  doors 
after  operations  are  completed,  and  expose  from  twenty-four  to 
thirty-six  hours  if  possible. 

13.  Never  reverse  the  order  of  procedure.  Always  pour  in  the 
water  first,  next  the  acid,  and  lastly  put  in  the  cyanid  in  bags. 

14.  The  operator  should  never  return  to  the  building  after  the 
first  fumes  begin  to  issue. 

15.  Everyone  connected  with  the  fumigation  should  constantly 
bear  in  mind  the  deadly  nature  of  the  cyanid  and  the  gas  and  be  con- 
versant with  the  process  and  the  necessity  of  caution  before  the  gas 
is  evolved. 

ORDER   OF   PROCEDURE    IN    FUMIGATION. 

Briefly,  the  fumigation  of  a  mill  or  granary  includes  the  following 
steps: 

1.  Measuring  the  mill  and  computing  the  amount  of  chemicals 
and  number  of  generators  required. 

'_'.  .Securing  the  chemicals  and  the  generating  jars. 

3.  Preparation  of  the  mill,  including  cleaning,  sealing  up  as  nearly 
air-tight  as  possible,  and  arrangement  for  ventilation  from  without 
after  the  conclusion  of  the  fumigation,  and  preparing  signs. 

4.  Distribution  of  jars  and  measuring  into  each  the  proper  amount 
of  water. 

5.  Breaking  up  the  cyanid  and  weighing  and  placing  it  in  3-pound 
lots  in  sacks,  temporarily  storing  it  in  tightly  covered  tin  cans, 
preferably  a  can  for  each  floor. 

6.  Measuring  out  the  acid  and  adding  to  water  in  jars. 

7.  Placing  a  bag  of  cyanid  in  each  jar,  beginning  with  the  top 
floor. 

8.  Tightly  closing  and  locking  the  building  and  seeing  that  all 
warning  signs  are  in  place,  and,  if  necessary,  stationing  a  watchman 
without  to  guard  the  building  from  entrance. 

9.  Opening  the  building  from  without  for  ventilation. 

10.  The  collection  and  disposal,  in  the  sewer  or  in  a  pit,  of  the 
residue,  the  cleaning  of  generators,  and  sweeping  out  dead  insects 
and  other  debris  before  resuming  work. 

[Cir.  112] 


21 

i  i  i  i  .   i    oi     BYDROCYANH     \(  n>   '.  \-    FUMIGATION    <  >x    SEED    MATERIA] 

A-  to  the  effect  of  hydrocyanic-acid  gas  on  the  germination  "f 
seeds,  a  series  of  tests  was  conducted  bj  l>r.  C.  0.  Townsend,  qom 
of  this  Department,  when  connected  with  the  Maryland  state  horti- 
cultural department,  with  1 1 1»>  resulting  conclusion  thai  drj  grains 
and  other  seeds  can  be  treated  with  hydrocyanic-acid  gas  for  insect 
pests  at  the  usual  strength  and  time,  or  even  for  several  days,  without 
ii>  jinv  \\;i\  poisoning  the  grain,  from  which  it  was  deduced  that  in 
the  ordinary  process  this  method  of  fumigation  can  be  employed 
without  injuring  seeds  either  for  planting  or  as  food.  Damp  grains 
and  other  seeds,  however,  are  more  susceptible  to  the  influence  of 
hydrocyanic-acid  gas,  and  some  precaution  must  be  observed  in  such 
cases  i  o  avoid  moist  ure. 

OTHER    REM!  DJJ  3. 

While  the  object  of  the  presenl  circular  is  to  furnish  information 
for  the  fumigation  of  mills  and  other  buildings  by  hydrocyanic-acid 
as  ;t  remedy  for  the  Sour  moth,  it  would  be  unwise  to  omit  stat- 
ing that  there  are  several  other  good  remedies,  which,  however,  are 
not  always  possible  <>f  application. 

Bisvlphid  of  carbon.  ( me  of  t  hese  is  bisulphid  of  carbon,  especially 
for  small  inclosures.  It  is  claimed  by  some  millers  to  be  of  value  f<>r 
■  first  fumigation,  following  with  hydrocyanic-acid  gas."  When 
forced  into  the  spouts,  machinery,  and  other  portions  of  the  mill,  it 
is  a  factor  in  killing  the  moth  and  other  insects. 

Cleanliness.  The  maintenance  of  scrupulous  cleanliness  through- 
out the  mill  undoubtedly  does  much  toward  preventing  tin'  introduc- 
tion of  the  flour  moth  as  well  as  in  restraining  its  increase  after  it 
has  once  obtained  a  foothold  in  the  mill.  Directions  for  cleaning 
have  been  given  on  page  13.     Prominent  millers  in  some  of  our  large 

cities,  6.  g.,  in  Louisville.  Ky.  ami  in  Kansas  City,  Mo.,  as  elsewhere. 
have  attributed  immunity  from  the  Hour  moth  to  the  facl  that  they 
maintain  the  most  rigid  system  of  cleanliness  in  their  mills. 

Sulphur  was  used  somewhat  extensively  as  a   remedy  for  the  flour 

moth  several  years  before  the  general  employment  of  hydrocyanic- 
acid  gas,  ami  it  is  still  valuable  ami  in  constant  use  by  millers  in  some 

State-.      Lack  of  space1  prevents  further  discussion  of  this  method. 

Freezing  is  an  inexpensive  and  valuable  remedy  where  practicable. 
Where  an  infested  mill  can  be  left  open  to  a  temperature  of  zero  or 
lower,  three  to  ten  nights  of  such  exposure  continuously  or  at  inter- 
tails  in  regard  t<>  tin-  employment  of  bisulphid  of  carbon  for  fumigating  build- 
ings are  given  in  Farmere'  Bulletin  No.  li">.  pp.  19  -'i»     Other  valuable  information 
riling  thi^  insecticide  i-*  also  furnished.    Copies  may  !"•  obtained  gratia  on  appli- 
cation t"  Members  of  Congress  "r  t>>  the  Secretary  of  Agriculture, 
[dr.  112] 


22 

vals  will  he  found  effective  in  destroying  the  flour  moth  in  its  dif- 
ferent stages,  unless  the  mill  or  other  huilding  happens  to  be  a  heated 
one.  The  moths  are  not  apt  to  breed  to  any  extent  during  the 
winter,  hence  there  are  few  eggs  to  deal  with  at  this  time.  In  north- 
ern mills  which  have  been  much  affected  by  tliis  insect,  especially  in 
Minnesota  and  Canada,  where  the  temperature  is  frequently  20°  to 
30°  F.  below  zero,  this  method  of  destroying  the  pest  has  been  pur- 
sued with  most  excellent  results.  Speaking  generally,  it  should  be 
practiced  wherever  the  temperature  warrants  the  process.  There  are, 
of  course,  southern  mills,  e.  g.,  in  Kansas  and  Texas,  where  this 
method  would  not  meet  with  much  success. 

Approved : 

James  Wilson, 

Secretary  of  Agriculture. 

Washington,  D.  C,  January  22,  1910. 

[Cir.  112] 

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